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/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * // Copyright (c) 1998, 2007, Oracle. All rights reserved.
 * 
 *
 * The contents of this file are subject to the terms of either the GNU
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 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
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 * 
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 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
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 * elects to include this software in this distribution under the [CDDL or GPL
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package oracle.toplink.essentials.internal.indirection;

import oracle.toplink.essentials.indirection.*;

/**
 * Used as the backup value holder in the unit of work for transparent indirection.
 * This ensure that a reference to the original value holder is held in case the
 * transparent collection or proxy is replace without first instantiating the original.
 *
 * @since 10.1.3
 * @author James Sutherland
 */
public class BackupValueHolder extends ValueHolder {

    /** Stores the original uow clone's value holder. */
    protected ValueHolderInterface unitOfWorkValueHolder;

    public BackupValueHolder(ValueHolderInterface unitOfWorkValueHolder) {
        this.unitOfWorkValueHolder = unitOfWorkValueHolder;
    }
    
    /**
     * If the original value holder was not instantiated,
     * then first instantiate it to obtain the backup value.
     */
    public Object getValue() {
        // Ensures instantiation of the original, and setting of this back value holder's value.
        getUnitOfWorkValueHolder().getValue();
        return value;
    }

    /**
     * Return the original uow clone's value holder.
     */
    public ValueHolderInterface getUnitOfWorkValueHolder() {
        return unitOfWorkValueHolder;
    }
}